Method and apparatus for optical micro manipulation

Abstract

A microscopic specimen such as a cell organelle or a tissue cell generally has a non-rotational symmetrical refractive index distribution. Converging onto the microscopic specimen a laser beam with a non-rotational symmetrical intensity distribution (an elliptical pattern) traps the specimen, with the direction of the major axis of the specimen aligned with the direction of the major axis of the elliptical pattern of the laser beam. This is because the laser beam with the non-rotational symmetrical refractive index distribution has a non-rotational symmetrical trapping force, and hence can trap the specimen with non-rotational symmetrical refractive index distribution in a dynamically reliable manner. Thus, rotation of the major axis of the intensity distribution of the laser beam causes rotation of the trapped specimen.

What is claimed is: 
     
       1. A method for optically micro-manipulating a specimen immersed in a liquid, comprising the steps of: generating a laser beam having a non-rotational symmetrical spatial property distribution;   converging the laser beam onto the immersed specimen to trap it;   controlling the spatial property distribution of the laser beam by rotating the laser beam; and   microscopically observing the specimen by means of a microscope.   
     
     
       2. The method according to claim 1, further comprising the steps of observing the specimen by the use of an optical system for radiating the laser beam onto the immersed specimen, and positioning the laser beam to the laser beam is emitted onto the specimen to trap it. 
     
     
       3. An apparatus for optically micro-manipulating a specimen to be microscopically examined by means of a microscope, comprising: means for generating a laser beam having a non-rotational symmetrical spatial property distribution;   means for converging the laser beam onto the specimen to trap it; and   means for rotating the laser beam about an optical axis thereof to control the spatial property distribution thereof.   
     
     
       4. The apparatus according to claim 3, wherein the laser beam generating means has a light source; means for converting a light beam, emitted from the light source, into a parallel light beam; and a filter located across the parallel light and having a non-rotational symmetrical aperture; and   the rotating means rotates the filter about the optical axis of the parallel light beam.   
     
     
       5. The apparatus according to claim 4, wherein the non-rotational symmetrical aperture is a rectangular aperture. 
     
     
       6. The apparatus according to claim 3, wherein the laser beam generating means has a laser source provided with a Fabry-Perot resonator; and a filter located in the resonator and having a non-rotational symmetrical aperture; and   the rotating means rotates the filter about the optical axis of a light beam passing in the resonator.   
     
     
       7. The apparatus according to claim 6, wherein the non-rotational symmetrical aperture is a rectangular aperture. 
     
     
       8. The apparatus according to claim 3, wherein the laser beam generating means has a laser source for emitting a linearly-polarized light beam. 
     
     
       9. The apparatus according to claim 8, wherein the rotating means has two λ/4 wave plates located across the light beam emitted from the laser source, and rotates about the axis of the light beam that one of the λ/4 wave plates which is located downstream of the other one in the direction of the light beam. 
     
     
       10. The apparatus according to claim 8, wherein the rotating means has a λ/2 wave plate located across the light beam emitted from the laser source, and rotates the λ/2 wave plate about the axis of the light beam. 
     
     
       11. An apparatus for optically micro-manipulating a specimen immersed in a liquid while microscopically observing the specimen, comprising: a container containing the liquid in which the specimen is immersed;   means for microscopically observing the specimen;   means for generating a laser beam having a non-rotational symmetrical spatial property distribution;   means for converging the laser beam onto the specimen to trap it; and   means for rotating the laser beam to control the spatial property distribution thereof.   
     
     
       12. The apparatus according to claim 11, wherein the converging means emits the laser beam into the container in a horizontal direction, and the microscopical observation means permits the specimen to be observed from above the container. 
     
     
       13. The apparatus according to claim 12, wherein the converging means converges two laser beams irradiated in opposite directions to each other, on the specimen. 
     
     
       14. The apparatus according to claim 11, further comprising: first image pick-up means for picking up an optical image of the specimen formed by the converging means;   second image pick-up means for picking up an optical image from the microscopic observation means; and   means for selectively displaying the optical images picked by the first and second image pick-up means.   
     
     
       15. The apparatus according to claim 11, wherein the converging means emits the laser beam from under the container, and the microscopic observation means permits the specimen to be observed in a horizontal direction for the container. 
     
     
       16. The apparatus according to claim 11, further comprising means for moving the container along a direction of the optical axis of the microscopic observation means. 
     
     
       17. The apparatus according to claim 11, further comprising means for moving the container along a direction of the optical axis of the converging means.